Determining when to initiate an intra- distributed storage unit rebuild vs. an inter- distributed storage unit rebuild

ABSTRACT

A method for execution by one or more processing modules of one or more computing devices of a dispersed storage network (DSN), the method begins by identifying an encoded data slice to be rebuilt within a DS unit, obtaining DS unit status information, selecting a rebuilding approach based on the DS unit status information, the rebuilding approach including an internal approach or an external approach. The method continues by obtaining, upon selecting the internal approach, internal rebuilding information from one or more memories of the DS unit and rebuilding the encoded data slice to be rebuilt utilizing the internal rebuilding information. The method continues by obtaining, upon selecting the external approach, external rebuilding information from at least a decode threshold number of other DS units of a set of DS units that includes the DS unit and rebuilding the encoded data slice to be rebuilt utilizing the external rebuilding information.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present U.S. Utility Patent Application claims priority pursuant to35 U.S.C. § 120, as a continuation-in-part (CIP) of U.S. Utility patentapplication Ser. No. 15/656,245, entitled “DETERMINING WHEN TO USECONVERGENT ENCRYPTION,” filed Jul. 21, 2017, which claims priority as acontinuation-in-part of U.S. Utility application Ser. No. 15/011,807entitled “RESOLVING WRITE CONFLICTS IN A DISPERSED STORAGE NETWORK”filed Feb. 1, 2016, issued as U.S. Pat. No. 9,766,810, on Sep. 19, 2017,which claims priority pursuant to 35 U.S.C. § 120 as a continuation ofU.S. Utility application Ser. No. 14/153,366, entitled “RESOLVING WRITECONFLICTS IN A DISPERSED STORAGE NETWORK”, filed Jan. 13, 2014, issuedas U.S. Pat. No. 9,274,908, on Mar. 1, 2016, which claims prioritypursuant to 35 U.S.C. § 119(e) to U.S. Provisional Application No.61/769,595, entitled “SECURELY STORING DATA WITHOUT DUPLICATION IN ADISPERSED STORAGE NETWORK”, filed Feb. 26, 2013, all of which are herebyincorporated herein by reference in their entirety and made part of thepresent U.S. Utility Patent Application for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION Technical Field of the Invention

This invention relates generally to computer networks and moreparticularly to dispersing error encoded data.

Description of Related Art

Computing devices are known to communicate data, process data, and/orstore data. Such computing devices range from wireless smart phones,laptops, tablets, personal computers (PC), work stations, and video gamedevices, to data centers that support millions of web searches, stocktrades, or on-line purchases every day. In general, a computing deviceincludes a central processing unit (CPU), a memory system, userinput/output interfaces, peripheral device interfaces, and aninterconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using“cloud computing” to perform one or more computing functions (e.g., aservice, an application, an algorithm, an arithmetic logic function,etc.) on behalf of the computer. Further, for large services,applications, and/or functions, cloud computing may be performed bymultiple cloud computing resources in a distributed manner to improvethe response time for completion of the service, application, and/orfunction. For example, Hadoop is an open source software framework thatsupports distributed applications enabling application execution bythousands of computers.

In addition to cloud computing, a computer may use “cloud storage” aspart of its memory system. As is known, cloud storage enables a user,via its computer, to store files, applications, etc. on an Internetstorage system. The Internet storage system may include a RAID(redundant array of independent disks) system and/or a dispersed storagesystem that uses an error correction scheme to encode data for storage.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a dispersed ordistributed storage network (DSN) in accordance with the presentinvention;

FIG. 2 is a schematic block diagram of an embodiment of a computing corein accordance with the present invention;

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data in accordance with the present invention;

FIG. 4 is a schematic block diagram of a generic example of an errorencoding function in accordance with the present invention;

FIG. 5 is a schematic block diagram of a specific example of an errorencoding function in accordance with the present invention;

FIG. 6 is a schematic block diagram of an example of a slice name of anencoded data slice (EDS) in accordance with the present invention;

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of data in accordance with the present invention;

FIG. 8 is a schematic block diagram of a generic example of an errordecoding function in accordance with the present invention;

FIG. 9 is a schematic block diagram of a dispersed storage networkmemory in accordance with the present invention; and

FIG. 9A is a flowchart illustrating an example of rebuilding a slice tobe rebuilt in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a dispersed, ordistributed, storage network (DSN) 10 that includes a plurality ofcomputing devices 12-16, a managing unit 18, an integrity processingunit 20, and a DSN memory 22. The components of the DSN 10 are coupledto a network 24, which may include one or more wireless and/or wirelined communication systems; one or more non-public intranet systemsand/or public internet systems; and/or one or more local area networks(LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of storage units 36 that may belocated at geographically different sites (e.g., one in Chicago, one inMilwaukee, etc.), at a common site, or a combination thereof. Forexample, if the DSN memory 22 includes eight storage units 36, eachstorage unit is located at a different site. As another example, if theDSN memory 22 includes eight storage units 36, all eight storage unitsare located at the same site. As yet another example, if the DSN memory22 includes eight storage units 36, a first pair of storage units are ata first common site, a second pair of storage units are at a secondcommon site, a third pair of storage units are at a third common site,and a fourth pair of storage units are at a fourth common site. Notethat a DSN memory 22 may include more or less than eight storage units36. Further note that each storage unit 36 includes a computing core (asshown in FIG. 2, or components thereof) and a plurality of memorydevices for storing dispersed error encoded data.

Each of the computing devices 12-16, the managing unit 18, and theintegrity processing unit 20 include a computing core 26, which includesnetwork interfaces 30-33. Computing devices 12-16 may each be a portablecomputing device and/or a fixed computing device. A portable computingdevice may be a social networking device, a gaming device, a cell phone,a smart phone, a digital assistant, a digital music player, a digitalvideo player, a laptop computer, a handheld computer, a tablet, a videogame controller, and/or any other portable device that includes acomputing core. A fixed computing device may be a computer (PC), acomputer server, a cable set-top box, a satellite receiver, a televisionset, a printer, a fax machine, home entertainment equipment, a videogame console, and/or any type of home or office computing equipment.Note that each of the managing unit 18 and the integrity processing unit20 may be separate computing devices, may be a common computing device,and/or may be integrated into one or more of the computing devices 12-16and/or into one or more of the storage units 36.

Each interface 30, 32, and 33 includes software and hardware to supportone or more communication links via the network 24 indirectly and/ordirectly. For example, interface 30 supports a communication link (e.g.,wired, wireless, direct, via a LAN, via the network 24, etc.) betweencomputing devices 14 and 16. As another example, interface 32 supportscommunication links (e.g., a wired connection, a wireless connection, aLAN connection, and/or any other type of connection to/from the network24) between computing devices 12 & 16 and the DSN memory 22. As yetanother example, interface 33 supports a communication link for each ofthe managing unit 18 and the integrity processing unit 20 to the network24.

Computing devices 12 and 16 include a dispersed storage (DS) clientmodule 34, which enables the computing device to dispersed storage errorencode and decode data as subsequently described with reference to oneor more of FIGS. 3-9A. In this example embodiment, computing device 16functions as a dispersed storage processing agent for computing device14. In this role, computing device 16 dispersed storage error encodesand decodes data on behalf of computing device 14. With the use ofdispersed storage error encoding and decoding, the DSN 10 is tolerant ofa significant number of storage unit failures (the number of failures isbased on parameters of the dispersed storage error encoding function)without loss of data and without the need for a redundant or backupcopies of the data. Further, the DSN 10 stores data for an indefiniteperiod of time without data loss and in a secure manner (e.g., thesystem is very resistant to unauthorized attempts at accessing thedata).

In operation, the managing unit 18 performs DS management services. Forexample, the managing unit 18 establishes distributed data storageparameters (e.g., vault creation, distributed storage parameters,security parameters, billing information, user profile information,etc.) for computing devices 12-14 individually or as part of a group ofuser devices. As a specific example, the managing unit 18 coordinatescreation of a vault (e.g., a virtual memory block associated with aportion of an overall namespace of the DSN) within the DSTN memory 22for a user device, a group of devices, or for public access andestablishes per vault dispersed storage (DS) error encoding parametersfor a vault. The managing unit 18 facilitates storage of DS errorencoding parameters for each vault by updating registry information ofthe DSN 10, where the registry information may be stored in the DSNmemory 22, a computing device 12-16, the managing unit 18, and/or theintegrity processing unit 20.

The DSN managing unit 18 creates and stores user profile information(e.g., an access control list (ACL)) in local memory and/or withinmemory of the DSN memory 22. The user profile information includesauthentication information, permissions, and/or the security parameters.The security parameters may include encryption/decryption scheme, one ormore encryption keys, key generation scheme, and/or dataencoding/decoding scheme.

The DSN managing unit 18 creates billing information for a particularuser, a user group, a vault access, public vault access, etc. Forinstance, the DSTN managing unit 18 tracks the number of times a useraccesses a non-public vault and/or public vaults, which can be used togenerate per-access billing information. In another instance, the DSTNmanaging unit 18 tracks the amount of data stored and/or retrieved by auser device and/or a user group, which can be used to generateper-data-amount billing information.

As another example, the managing unit 18 performs network operations,network administration, and/or network maintenance. Network operationsincludes authenticating user data allocation requests (e.g., read and/orwrite requests), managing creation of vaults, establishingauthentication credentials for user devices, adding/deleting components(e.g., user devices, storage units, and/or computing devices with a DSclient module 34) to/from the DSN 10, and/or establishing authenticationcredentials for the storage units 36. Network administration includesmonitoring devices and/or units for failures, maintaining vaultinformation, determining device and/or unit activation status,determining device and/or unit loading, and/or determining any othersystem level operation that affects the performance level of the DSN 10.Network maintenance includes facilitating replacing, upgrading,repairing, and/or expanding a device and/or unit of the DSN 10.

The integrity processing unit 20 performs rebuilding of ‘bad’ or missingencoded data slices. At a high level, the integrity processing unit 20performs rebuilding by periodically attempting to retrieve/list encodeddata slices, and/or slice names of the encoded data slices, from the DSNmemory 22. For retrieved encoded slices, they are checked for errors dueto data corruption, outdated version, etc. If a slice includes an error,it is flagged as a ‘bad’ slice. For encoded data slices that were notreceived and/or not listed, they are flagged as missing slices. Badand/or missing slices are subsequently rebuilt using other retrievedencoded data slices that are deemed to be good slices to produce rebuiltslices. The rebuilt slices are stored in the DSTN memory 22.

FIG. 2 is a schematic block diagram of an embodiment of a computing core26 that includes a processing module 50, a memory controller 52, mainmemory 54, a video graphics processing unit 55, an input/output (IO)controller 56, a peripheral component interconnect (PCI) interface 58,an IO interface module 60, at least one IO device interface module 62, aread only memory (ROM) basic input output system (BIOS) 64, and one ormore memory interface modules. The one or more memory interfacemodule(s) includes one or more of a universal serial bus (USB) interfacemodule 66, a host bus adapter (HBA) interface module 68, a networkinterface module 70, a flash interface module 72, a hard drive interfacemodule 74, and a DSN interface module 76.

The DSN interface module 76 functions to mimic a conventional operatingsystem (OS) file system interface (e.g., network file system (NFS),flash file system (FFS), disk file system (DFS), file transfer protocol(FTP), web-based distributed authoring and versioning (WebDAV), etc.)and/or a block memory interface (e.g., small computer system interface(SCSI), internet small computer system interface (iSCSI), etc.). The DSNinterface module 76 and/or the network interface module 70 may functionas one or more of the interface 30-33 of FIG. 1. Note that the IO deviceinterface module 62 and/or the memory interface modules 66-76 may becollectively or individually referred to as IO ports.

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data. When a computing device 12 or 16 has data tostore it disperse storage error encodes the data in accordance with adispersed storage error encoding process based on dispersed storageerror encoding parameters. The dispersed storage error encodingparameters include an encoding function (e.g., information dispersalalgorithm, Reed-Solomon, Cauchy Reed-Solomon, systematic encoding,non-systematic encoding, on-line codes, etc.), a data segmentingprotocol (e.g., data segment size, fixed, variable, etc.), and per datasegment encoding values. The per data segment encoding values include atotal, or pillar width, number (T) of encoded data slices per encodingof a data segment i.e., in a set of encoded data slices); a decodethreshold number (D) of encoded data slices of a set of encoded dataslices that are needed to recover the data segment; a read thresholdnumber (R) of encoded data slices to indicate a number of encoded dataslices per set to be read from storage for decoding of the data segment;and/or a write threshold number (W) to indicate a number of encoded dataslices per set that must be accurately stored before the encoded datasegment is deemed to have been properly stored. The dispersed storageerror encoding parameters may further include slicing information (e.g.,the number of encoded data slices that will be created for each datasegment) and/or slice security information (e.g., per encoded data sliceencryption, compression, integrity checksum, etc.).

In the present example, Cauchy Reed-Solomon has been selected as theencoding function (a generic example is shown in FIG. 4 and a specificexample is shown in FIG. 5); the data segmenting protocol is to dividethe data object into fixed sized data segments; and the per data segmentencoding values include: a pillar width of 5, a decode threshold of 3, aread threshold of 4, and a write threshold of 4. In accordance with thedata segmenting protocol, the computing device 12 or 16 divides the data(e.g., a file (e.g., text, video, audio, etc.), a data object, or otherdata arrangement) into a plurality of fixed sized data segments (e.g., 1through Y of a fixed size in range of Kilo-bytes to Tera-bytes or more).The number of data segments created is dependent of the size of the dataand the data segmenting protocol.

The computing device 12 or 16 then disperse storage error encodes a datasegment using the selected encoding function (e.g., Cauchy Reed-Solomon)to produce a set of encoded data slices. FIG. 4 illustrates a genericCauchy Reed-Solomon encoding function, which includes an encoding matrix(EM), a data matrix (DM), and a coded matrix (CM). The size of theencoding matrix (EM) is dependent on the pillar width number (T) and thedecode threshold number (D) of selected per data segment encodingvalues. To produce the data matrix (DM), the data segment is dividedinto a plurality of data blocks and the data blocks are arranged into Dnumber of rows with Z data blocks per row. Note that Z is a function ofthe number of data blocks created from the data segment and the decodethreshold number (D). The coded matrix is produced by matrix multiplyingthe data matrix by the encoding matrix.

FIG. 5 illustrates a specific example of Cauchy Reed-Solomon encodingwith a pillar number (T) of five and decode threshold number of three.In this example, a first data segment is divided into twelve data blocks(D1-D12). The coded matrix includes five rows of coded data blocks,where the first row of X11-X14 corresponds to a first encoded data slice(EDS 1_1), the second row of X21-X24 corresponds to a second encodeddata slice (EDS 2_1), the third row of X31-X34 corresponds to a thirdencoded data slice (EDS 3_1), the fourth row of X41-X44 corresponds to afourth encoded data slice (EDS 4_1), and the fifth row of X51-X54corresponds to a fifth encoded data slice (EDS 5_1). Note that thesecond number of the EDS designation corresponds to the data segmentnumber.

Returning to the discussion of FIG. 3, the computing device also createsa slice name (SN) for each encoded data slice (EDS) in the set ofencoded data slices. A typical format for a slice name 60 is shown inFIG. 6. As shown, the slice name (SN) 60 includes a pillar number of theencoded data slice (e.g., one of 1-T), a data segment number (e.g., oneof 1-Y), a vault identifier (ID), a data object identifier (ID), and mayfurther include revision level information of the encoded data slices.The slice name functions as, at least part of, a DSN address for theencoded data slice for storage and retrieval from the DSN memory 22.

As a result of encoding, the computing device 12 or 16 produces aplurality of sets of encoded data slices, which are provided with theirrespective slice names to the storage units for storage. As shown, thefirst set of encoded data slices includes EDS 1_1 through EDS 5_1 andthe first set of slice names includes SN 1_1 through SN 5_1 and the lastset of encoded data slices includes EDS 1_Y through EDS 5_Y and the lastset of slice names includes SN 1_Y through SN 5_Y.

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of a data object that was dispersed storage error encodedand stored in the example of FIG. 4. In this example, the computingdevice 12 or 16 retrieves from the storage units at least the decodethreshold number of encoded data slices per data segment. As a specificexample, the computing device retrieves a read threshold number ofencoded data slices.

To recover a data segment from a decode threshold number of encoded dataslices, the computing device uses a decoding function as shown in FIG.8. As shown, the decoding function is essentially an inverse of theencoding function of FIG. 4. The coded matrix includes a decodethreshold number of rows (e.g., three in this example) and the decodingmatrix in an inversion of the encoding matrix that includes thecorresponding rows of the coded matrix. For example, if the coded matrixincludes rows 1, 2, and 4, the encoding matrix is reduced to rows 1, 2,and 4, and then inverted to produce the decoding matrix.

Within a DS unit, a set of memory devices may be arranged in a mode ofstriping with optional parity. This enables a greater overall throughputto access of slices within the DS unit as multiple disks each contributea smaller proportion of the overall content. In addition, in the eventof a drive failure, the drive may be rebuilt from the additional parityinformation and the additional drives without having to contact other DSunits. If there are multiple drive failures beyond the capacity for theRAID parity to recover, then an inter-DS unit rebuild must be initiated.When network communication is down, only an intra-DS unit rebuild ispossible. In one embodiment, when both possibilities are available, adetermination of whether to execute an intra- vs. an inter-ds unitrebuild is made. This determination may be made based on a performancerequirement, a bandwidth cost, internal I/O (input/output) load of thedevice, available CPU resources, and other related factors. For example,if a rebalancing operation is occurring causing heavy internal memorydevice utilization, the DS unit may opt for an inter-DS unit rebuild asopposed to an intra-DS unit rebuild. If, on the other hand, the DS unitis on a WAN and bandwidth is expensive, it may tend to prefer anintra-DS unit rebuild.

FIG. 9 is a schematic block diagram of a dispersed storage network (DSN)memory 500 that includes a plurality of the dispersed storage (DS) units354. The plurality of DS units 354 includes at least one DS unit setthat includes a DS unit 354 and other DS units 502 of the DS unit set.The DS unit 354 includes a controller 504, a plurality of main memories506, and a plurality of internal integrity memories 508. The DSN memory500 functions to rebuild an encoded data slice to be rebuilt, where theencoded data slice to be rebuilt is associated with a main memory 506 ofthe plurality of main memories. Data is encoded using at least one of adispersed storage error coding function or a redundant array ofindependent disks (RAID) coding function to produce rebuildinginformation, where recovery of the encoded data slice to be rebuilt isenabled by retrieving a threshold number of rebuilding elements of therebuilding information. The rebuilding elements include one or more ofparity information or other encoded data slices of a set of encoded dataslices that includes the encoded data slice to be rebuilt. DSN memory500 and DS units 354 can be implemented using DSN memory 22 and storageunits 36, respectively, as illustrated in FIG. 1

In an example of operation, the controller 504 identifies the encodeddata slice to be rebuilt. The identifying includes a variety ofapproaches. A first approach includes indicating that the encoded dataslice to be rebuilt requires rebuilding when a calculated integrityvalue of the encoded data slice to be rebuilt compares unfavorably to aretrieved integrity value associated with the encoded data slice to berebuilt, where the retrieved integrity value is retrieved from anassociated internal integrity memory. A second approach includesreceiving an error message that includes an identifier of the encodeddata slice to be rebuilt. A third approach includes receiving arebuilding request that includes the identifier of the encoded dataslice to be rebuilt.

Having identified the encoded data slice to be rebuilt, the controller504 selects a rebuilding approach as one of an internal approach or anexternal approach. The selecting may be based on one or more of networktraffic level, a main memory availability indicator, an internalintegrity memory availability indicator, a number of available other DSunits of the DS unit set, a performance requirement, estimated networktraffic costs, a controller loading level, available control resources,or an active rebalancing operation status. The internal approach isassociated with utilizing rebuilding information from at least athreshold number of internal integrity memories of the plurality ofinternal integrity memories. The external approach is associated withutilizing rebuilding information from at least a threshold number ofother DS units of the DS unit set. For example, the controller 504selects the internal approach when estimated network traffic costs aregreater than a cost threshold. As another example, the controller 504selects the external approach when the controller loading level isgreater than a loading level threshold.

When the selected rebuilding approach includes the internal approach,the controller 504 retrieves a threshold number of rebuilding elementsfrom the threshold number of internal integrity memories 508. Forexample, the controller 504 retrieves a threshold number of data blocksand/or parity blocks of a common data slice that includes the encodeddata slice to be rebuilt when the RAID function is utilized. As anotherexample, the controller 504 retrieves a threshold number of encoded dataslices of the set of encoded data slices that includes the encoded dataslice to be rebuilt from the threshold number of internal integritymemories 508 when the dispersed storage error coding function isutilized. The controller 504 decodes the threshold number of rebuildingelements to produce a rebuilt encoded data slice.

When the selected rebuilding approach includes the external approach,the controller 504 retrieves the threshold number of rebuilding elementsfrom the threshold number of other DS units of the DS unit set 502. Forexample, the controller 504 issues read slice requests 510 and receivesread slice responses 512 to retrieve the threshold number of encodeddata slices of the set of encoded data slices that includes the encodeddata slice to be rebuilt from the threshold number of other DS units ofthe DS unit set when the dispersed storage error coding function isutilized. The controller decodes the threshold number of rebuildingelements to produce the rebuilt encoded data slice.

FIG. 9A is a flowchart illustrating an example of rebuilding a slice tobe rebuilt. The method begins at step 514 where a processing module(e.g., of a dispersed storage (DS) processing module) identifies a sliceto be rebuilt associated with a DS unit. The identifying includes atleast one of receiving an error message, comparing storage integrityinformation to calculated integrity information, or comparing a slicename list from the DS unit and from other DS units of a DS unit set thatincludes the DS unit. The method continues at step 516 where theprocessing module obtains DS unit status information. The DS unit statusinformation includes one or more of a network traffic level, a number ofavailable other DS units of the DS unit set, estimated network trafficcosts, a loading level of the DS unit, available resources of the DSunit, or active operation types of the DS unit.

The method continues at step 518 where the processing module selects arebuilding approach based on the DS unit status information. Therebuilding approach includes one of an internal approach and an externalapproach. The internal approach is associated with utilizing rebuildinginformation from one or more memories (e.g., a threshold number) of theDS unit. The external approach is associated with utilizing rebuildinginformation from at least a threshold number of other DS units of the DSunit set where data is encoded using a dispersed storage error codingfunction to produce a set of encoded data slices, including the encodeddata slice to be rebuilt, that are stored in the DS unit set. The methodbranches to step 524 when the processing module selects the externalapproach. The method continues to step 520 when the processing moduleselects the internal approach.

The method continues at step 520 where the processing module obtainsinternal rebuilding information from one or more memories of the DS unitwhen the internal approach is selected. The internal rebuildinginformation includes at least one of a threshold number of encoded dataslices of the set of encoded data slices when the dispersed storageerror coding function is utilized and a threshold number of data blocksand parity blocks when a redundant array of independent disks (RAID)function is utilized. For example, the processing module retrieves thethreshold number of data blocks and parity blocks from a thresholdnumber of memories of the DS unit when the RAID function is utilized. Asanother example, the processing module retrieves the threshold number ofencoded data slices from the threshold number of memories of the DS unitwhen the dispersed storage error coding function is utilized. Thedispersed storage error coding function and the RAID function may beutilized in accordance with a storage approach. The processing modulemay further determine the storage approach based on one or more ofreceiving the storage approach, a lookup, and selecting the storageapproach based on storage requirements when initially storing data.

The method continues at step 522 where the processing module rebuildsthe encoded data slice to be rebuilt utilizing the internal rebuildinginformation. For example, the processing module decodes the retrievedthreshold number of encoded data slices using the dispersed storageerror coding function to produce a rebuilt slice. As another example,the processing module utilizes the RAID function on the threshold numberof data blocks and parity blocks to produce the rebuilt slice.

The method continues at step 524 where the processing module obtainsexternal rebuilding information from at least a decode threshold numberof other DS units of the set of DS units that includes the DS unit whenthe processing module selects the external approach. The obtainingincludes issuing at least a decode threshold number of reads slicerequests to the other DS units and receiving at least a decode thresholdnumber of read slice responses. The method continues at step 526 wherethe processing module rebuilds the slice to be rebuilt utilizing theexternal rebuilding information. For example, the processing moduledecodes at least a decode threshold number of encoded data slices fromthe at least a decode threshold number of received read slice responsesto produce the slice to be rebuilt.

The method described above in conjunction with the processing module canalternatively be performed by other modules of the dispersed storagenetwork or by other computing devices. In addition, at least one memorysection (e.g., a non-transitory computer readable storage medium) thatstores operational instructions can, when executed by one or moreprocessing modules of one or more computing devices of the dispersedstorage network (DSN), cause the one or more computing devices toperform any or all of the method steps described above.

It is noted that terminologies as may be used herein such as bit stream,stream, signal sequence, etc. (or their equivalents) have been usedinterchangeably to describe digital information whose contentcorresponds to any of a number of desired types (e.g., data, video,speech, audio, etc. any of which may generally be referred to as‘data’).

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “configured to”, “operably coupled to”, “coupled to”, and/or“coupling” includes direct coupling between items and/or indirectcoupling between items via an intervening item (e.g., an item includes,but is not limited to, a component, an element, a circuit, and/or amodule) where, for an example of indirect coupling, the intervening itemdoes not modify the information of a signal but may adjust its currentlevel, voltage level, and/or power level. As may further be used herein,inferred coupling (i.e., where one element is coupled to another elementby inference) includes direct and indirect coupling between two items inthe same manner as “coupled to”. As may even further be used herein, theterm “configured to”, “operable to”, “coupled to”, or “operably coupledto” indicates that an item includes one or more of power connections,input(s), output(s), etc., to perform, when activated, one or more itscorresponding functions and may further include inferred coupling to oneor more other items. As may still further be used herein, the term“associated with”, includes direct and/or indirect coupling of separateitems and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that acomparison between two or more items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signal1 has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1. As maybe used herein, the term “compares unfavorably”, indicates that acomparison between two or more items, signals, etc., fails to providethe desired relationship.

As may also be used herein, the terms “processing module”, “processingcircuit”, “processor”, and/or “processing unit” may be a singleprocessing device or a plurality of processing devices. Such aprocessing device may be a microprocessor, micro-controller, digitalsignal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on hard coding of thecircuitry and/or operational instructions. The processing module,module, processing circuit, and/or processing unit may be, or furtherinclude, memory and/or an integrated memory element, which may be asingle memory device, a plurality of memory devices, and/or embeddedcircuitry of another processing module, module, processing circuit,and/or processing unit. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module,module, processing circuit, and/or processing unit includes more thanone processing device, the processing devices may be centrally located(e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that if the processing module, module, processing circuit,and/or processing unit implements one or more of its functions via astate machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory and/or memory element storing the correspondingoperational instructions may be embedded within, or external to, thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry. Still further note that, the memoryelement may store, and the processing module, module, processingcircuit, and/or processing unit executes, hard coded and/or operationalinstructions corresponding to at least some of the steps and/orfunctions illustrated in one or more of the Figures. Such a memorydevice or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claims. Further, the boundariesof these functional building blocks have been arbitrarily defined forconvenience of description. Alternate boundaries could be defined aslong as the certain significant functions are appropriately performed.Similarly, flow diagram blocks may also have been arbitrarily definedherein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence couldhave been defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claims. One of average skill in the art will alsorecognize that the functional building blocks, and other illustrativeblocks, modules and components herein, can be implemented as illustratedor by discrete components, application specific integrated circuits,processors executing appropriate software and the like or anycombination thereof.

In addition, a flow diagram may include a “start” and/or “continue”indication. The “start” and “continue” indications reflect that thesteps presented can optionally be incorporated in or otherwise used inconjunction with other routines. In this context, “start” indicates thebeginning of the first step presented and may be preceded by otheractivities not specifically shown. Further, the “continue” indicationreflects that the steps presented may be performed multiple times and/ormay be succeeded by other activities not specifically shown. Further,while a flow diagram indicates a particular ordering of steps, otherorderings are likewise possible provided that the principles ofcausality are maintained.

The one or more embodiments are used herein to illustrate one or moreaspects, one or more features, one or more concepts, and/or one or moreexamples. A physical embodiment of an apparatus, an article ofmanufacture, a machine, and/or of a process may include one or more ofthe aspects, features, concepts, examples, etc. described with referenceto one or more of the embodiments discussed herein. Further, from figureto figure, the embodiments may incorporate the same or similarly namedfunctions, steps, modules, etc. that may use the same or differentreference numbers and, as such, the functions, steps, modules, etc. maybe the same or similar functions, steps, modules, etc. or differentones.

Unless specifically stated to the contra, signals to, from, and/orbetween elements in a figure of any of the figures presented herein maybe analog or digital, continuous time or discrete time, and single-endedor differential. For instance, if a signal path is shown as asingle-ended path, it also represents a differential signal path.Similarly, if a signal path is shown as a differential path, it alsorepresents a single-ended signal path. While one or more particulararchitectures are described herein, other architectures can likewise beimplemented that use one or more data buses not expressly shown, directconnectivity between elements, and/or indirect coupling between otherelements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of theembodiments. A module implements one or more functions via a device suchas a processor or other processing device or other hardware that mayinclude or operate in association with a memory that stores operationalinstructions. A module may operate independently and/or in conjunctionwith software and/or firmware. As also used herein, a module may containone or more sub-modules, each of which may be one or more modules.

As may further be used herein, a computer readable memory includes oneor more memory elements. A memory element may be a separate memorydevice, multiple memory devices, or a set of memory locations within amemory device. Such a memory device may be a read-only memory, randomaccess memory, volatile memory, non-volatile memory, static memory,dynamic memory, flash memory, cache memory, and/or any device thatstores digital information. The memory device may be in a form a solidstate memory, a hard drive memory, cloud memory, thumb drive, servermemory, computing device memory, and/or other physical medium forstoring digital information.

While particular combinations of various functions and features of theone or more embodiments have been expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent disclosure is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

What is claimed is:
 1. A method for execution by one or more processingmodules of one or more computing devices of a dispersed storage network(DSN), the method comprises: identifying an encoded data slice to berebuilt within a dispersed storage (DS) unit; obtaining statusinformation of the DS unit; selecting a rebuilding approach based on thestatus information, the rebuilding approach including an internalapproach or an external approach; obtaining, upon selecting the internalapproach, internal rebuilding information from one or more memories ofthe DS unit; and rebuilding the encoded data slice to be rebuiltutilizing the internal rebuilding information; obtaining, upon selectingthe external approach, external rebuilding information from at least adecode threshold number of other DS units of a set of DS units thatincludes the DS unit; and rebuilding the encoded data slice to berebuilt utilizing the external rebuilding information.
 2. The method ofclaim 1, wherein the identifying includes at least one of: receiving anerror message, comparing storage integrity information to calculatedintegrity information, or comparing a slice name list from the DS unitand from other DS units of a DS unit set that includes the DS unit. 3.The method of claim 1, wherein the status information includes one ormore of: a network traffic level, a number of available other DS unitsof the set of DS units, estimated network traffic costs, a loading levelof the DS unit, available resources of the DS unit, or active operationtypes of the DS unit.
 4. The method of claim 1, wherein the internalapproach is associated with utilizing the internal rebuildinginformation from one or more memories within the DS unit.
 5. The methodof claim 4, wherein the internal rebuilding information includes athreshold number.
 6. The method of claim 1, wherein the internalrebuilding information includes at least one of: a threshold number ofencoded data slices of a set of encoded data slices when a dispersedstorage error coding function is utilized and a threshold number of datablocks or parity blocks when a redundant array of independent disks(RAID) function is utilized.
 7. The method of claim 6, wherein theinternal rebuilding information includes retrieving a threshold numberof data blocks and parity blocks from a threshold number of memories ofthe DS unit when the redundant array of independent disks (RAID)function is utilized.
 8. The method of claim 1, wherein the internalrebuilding information includes retrieving a threshold number of encodeddata slices from a threshold number of memories of the DS unit when adispersed storage error coding function is utilized.
 9. The method ofclaim 1, wherein the external approach includes utilizing the externalrebuilding information for at least a threshold number of other DS unitsof the set of DS units, where data is encoded using a dispersed storageerror coding function to produce a set of encoded data slices, includingthe encoded data slice to be rebuilt, that are stored in the set of DSunits.
 10. The method of claim 9, wherein the rebuilding includesdecoding a retrieved threshold number of encoded data slices using adispersed storage error coding function to produce a rebuilt slice. 11.The method of claim 1 further comprises determining a storage approachfor the DS unit based on one or more of receiving the storage approach,a lookup, or selecting the storage approach based on storagerequirements when initially storing data.
 12. The method of claim 1,wherein the rebuilding the encoded data slice to be rebuilt utilizingthe internal rebuilding information includes utilizing a RAID functionon a threshold number of data blocks and parity blocks to produce therebuilt encoded data slice.
 13. The method of claim 1, wherein theobtain external rebuilding information includes issuing at least adecode threshold number of reads slice requests to other DS units andreceiving at least a decode threshold number of read slice responses.14. The method of claim 13, wherein the rebuilding the encoded dataslice to be rebuilt utilizing the external rebuilding informationincludes decoding at least a decode threshold number of encoded dataslices from the at least a decode threshold number of received readslice responses to produce the encoded data slice to be rebuilt.
 15. Acomputing device of a group of computing devices of a dispersed storagenetwork (DSN), the computing device comprises: an interface; a localmemory; and a processing module operably coupled to the interface andthe local memory, wherein the processing module functions to: identifyan encoded data slice to be rebuilt within a dispersed storage (DS)unit; obtain status information of the DS unit; select a rebuildingapproach based on the status information, the rebuilding approachincluding an internal approach or an external approach; obtain, uponselecting the internal approach, internal rebuilding information fromone or more memories of the DS unit; and rebuild the encoded data sliceto be rebuilt utilizing the internal rebuilding information; obtain,upon selecting the external approach, external rebuilding informationfrom at least a decode threshold number of other DS units of a set of DSunits that includes the DS unit; and rebuild the encoded data slice tobe rebuilt utilizing the external rebuilding information.
 16. Thecomputing device of claim 15, wherein the status information includesone or more of: a network traffic level, a number of available other DSunits of the set of DS units, estimated network traffic costs, a loadinglevel of the DS unit, available resources of the DS unit, or activeoperation types of the DS unit.
 17. The computing device of claim 15,wherein the external approach includes utilizing the external rebuildinginformation for at least a threshold number of other DS units of the setof DS units, where data is encoded using a dispersed storage errorcoding function to produce a set of encoded data slices, including theencoded data slice to be rebuilt, that are stored in the set of DSunits.
 18. The computing device of claim 15, wherein the internalrebuilding information includes at least one of: a threshold number ofencoded data slices of a set of encoded data slices when a dispersedstorage error coding function is utilized and a threshold number of datablocks and parity blocks when a redundant array of independent disks(RAID) function is utilized.
 19. The computing device of claim 15,wherein the obtain external rebuilding information includes issuing atleast a decode threshold number of reads slice requests to other DSunits and receiving at least a decode threshold number of read sliceresponses.
 20. A system comprises: an interface; a local memory; and aprocessing module operably coupled to the interface and the localmemory, wherein the processing module functions to: identify an encodeddata slice to be rebuilt within a dispersed storage (DS) unit; obtainstatus information of the DS unit; select a rebuilding approach based onthe status information, the rebuilding approach including an internalapproach or an external approach; obtain, upon selecting the internalapproach, internal rebuilding information from one or more memories ofthe DS unit; and rebuild the encoded data slice to be rebuilt utilizingthe internal rebuilding information; obtain, upon selecting the externalapproach, external rebuilding information from at least a decodethreshold number of other DS units of a set of DS units that includesthe DS unit; and rebuild the encoded data slice to be rebuilt utilizingthe external rebuilding information.